Electronic thermostat for fridge

[Bob 04 H260]

I know a number of you have replaced your mechanical thermostat with an electronic one from China. I bought one through Amazon to do the same. It does not indicate the polarity of the inout power on pins 3 and 4, either on the case or instruction sheet. If anyone has used one like the one in the picture I would appreciate any information you could provide.

Bob

Ps I tried to open it up but it appears to be glued tight !

 

[Ralph Johnstone]

Given there are no polarity markings on pins 3 and 4, I would assume these are the ON/OFF contacts (no polarity) to your compressor relay. Just to be sure, connect 12V to your other contacts (+ and -) amd then check for conductivity on pins 3 and 4 as you raise and lower the set point. Should make and break.

But far more important (to me anyway), is that the stat looks fairly bulky. How will you be installing it in the cooling compartment ? I'm looking at a failing stat as well and will be replacing with an electronic unit.

 

[Don Lucas]

I've got one of those I got to run my spillover fan. Far as I know it is just a contact.

I don't think I would install it in the compressor circuit unless you put a resistor in it to match the thermostat your system had (probably just affects the efficiency though).

 

[Bob 04 H260]

I am going to use it to turn the spill over fan on and off. The mechanical thermostat turns off at 40* and on at 34* too much hysteresis. I will mount this one outside the fridge under overhead galley cabinets, the temp probe obviously will be in the refrigerator compartment.

It is designed to run on 12 volts. It has two terminals for power in, neither has any polarity markings. The sheet indicates they are for power in but does indicate polarity either.

These are marketed under a variety of names but are either made in the same factory or they are cloning each other.

Bob

 

[Ralph Johnstone]

The mechanical thermostat turns off at 40* and on at 34* too much hysteresis.

Bob ................. maybe that's a bit excessive for the hysteresis (dead band) of the mechanical stat. Have you looked at the dead band for your electronic unit or is it adjustable (way too much to hope for) ?

Don't know if this is the one you purchased but as you've said, there is an endless supply of these things on the market under different names and all looking identical. The one I found goes by the name Lemonbest and that is one scary, scary, name.

Given that this is not part of a critical boat system and can be easily controlled by hand for a few days if the need arises (OFF/ON breaker) I've ordered one just to give it a try. If it fails ......... no great loss but definitely worth a try.

Thanks for the idea.

 

[Bob 04 H260]

Ralph, yes the electronic thermostat has adjustable hysteresis and was one of the reasons I ordered it. The picture of yours looks identical to mine, note the power input terminals, 3 & 4, do not indicate the polarity ! Almost cheap enough to just try it and see . I just don't have the time to wait for another one. Delivery on the last one was 3 weeks. You might want to order two !

I hoped to get this installed so it would be easy to set the temperature on the fridge, maybe save some AHrs and not worry about freezing the salad. Right now it seems it always needs a little touch, either too cold or too warm.

Maybe I'll hear back from the factory.

Thanks, Bob

 

[Ralph Johnstone]

Ralph, yes the electronic thermostat has adjustable hysteresis and was one of the reasons I ordered it.

Ajustable dead band ............ my prayers have been answered.

Can you please give me the brand name of the unit you have pictured ? Too small to read.

I may wind up with the other one I've ordered having adjustable dead band as well. But at that price, big deal:dance:. Delivery time from China is several weeks which I'm sure will grow into a month or better.

 

[Bob 04 H260]

Ralph, here are a couple of pictures, should help, good luck ! Bob

 

[Ralph Johnstone]

Ralph, here are a couple of pictures, should help, good luck ! Bob

Thanks Bob. It's on order, even if it is a dollar more.

 

[Rich Stidger]

I found a controller that looks a lot like the ones pictured here and the polarity is indicated.

http://www.autospeed.com/cms/article.html?&title=25-Temperature-Controller-and-Display&A=112617

 

[Ralph Johnstone]

Yipes ........................

.............. that's over double what I paid for this one and no shipping charge.

There are more of these things out there which "look" identical to each other than you can shake a stick at.

I don't really expect a lot to come from ordering one of these stats but at these prices, you can't go too far wrong even if it doesn't work at all. You can be sure I'll be watching this thing like a hawk for the first little while. At least I'll have a temp. readout to monitor the stat rather than the previous one which made beersicles and froze the lettuce.

Who knows, it may just work ............... stranger things have happened.

 

[Bob 04 H260]

I found a controller that looks a lot like the ones pictured here and the polarity is indicated.

http://www.autospeed.com/cms/article.html?&title=25-Temperature-Controller-and-Display&A=112617

Thanks For taking the time Rich ! Much appreciated, Bob

 

[Bob 04 H260]

Rich you did it !

Thanks again, it works !

Next job wire it into the refrigerator. That may have to wait until we get to the Bahamas. Too much to do right now to start another project.

Bob

 

[Rich Stidger]

Thanks again, it works !

Next job wire it into the refrigerator. That may have to wait until we get to the Bahamas. Too much to do right now to start another project.

Bob

No thanks needed. Google (and persistence) is your friend.

 

[Rick Templeton]

Sorry, don't want to change the track but was wondering if you are talking about replacing the temp controller in a standard freezer/fridge. I have a 1998 340 which has an Adler barber(?) top load unit. While tossing a bag of ice in I cracked the dial type controller on the upper right side of the box. I cant find a replacement but if one of these digital controllers can be used it would solve my problem. If so is it more or less plug and play or is there rewiring required.

Thanks in advance

 

[Bob 04 H260]

Hi Rick, no problem. We are talking about using this to replace a thermostat that controls a spillover fan between the freezer and refrigerator boxes in a top loading setup. These electronic thermostats can switch 5 amps, so no problem for the small fan. If you wanted to use it to switch the AB compressor a generic 12 volt automotive relay would work fine with it to do that.
Good luck, Bob

 

[Rick Templeton]

Thanks Bob,
I went ahead and ordered the controller based on my limited knowledge and your thread. Not sure if the controller I broke controlled the spill over fan or the compressor but I'll get it figured out eventually. Thanks for your response.

 

[Steve Feinsilver]

Why not use this to turn compressor on and off? Believe my fridge takes max 4 A at 12 V, this is rated at 5 A at 220V, should be OK, no?

 

[artboas]

Thermostat resistance

I've got one of those I got to run my spillover fan. Far as I know it is just a contact.

I don't think I would install it in the compressor circuit unless you put a resistor in it to match the thermostat your system had (probably just affects the efficiency though).

Don,

Thermostats are just bi-metalic strips.
The resistance should be close to zero ohms in closed position.
If you know something different, I'm interested to know.

 

[Don Lucas]

Don,

Thermostats are just bi-metalic strips.
The resistance should be close to zero ohms in closed position.
If you know something different, I'm interested to know.

AB thermostats have resistors in them that are matched to the size of the evaporator and determine the speed of the compressor